target/arm: Implement MVE VCTP

Implement the MVE VCTP insn, which sets the VPR.P0 predicate bits so
as to predicate any element at index Rn or greater is predicated.  As
with VPNOT, this insn itself is predicable and subject to beatwise
execution.

The calculation of the mask is the same as is used to determine
ltpmask in mve_element_mask(), but we precalculate masklen in
generated code to avoid having to have 4 helpers specialized by size.

We put the decode line in with the low-overhead-loop insns in
t32.decode because it's logically part of that collection of insn
patterns, even though it is an MVE only insn.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

diff --git a/target/arm/helper-mve.h b/target/arm/helper-mve.h
index 8cb941912fc333e3dbbf40e14628b6a77fae7bbd..b6cf3f0c94d5bf7788df5c50c8448d4f6bcff6b3 100644 (file)
--- a/target/arm/helper-mve.h
+++ b/target/arm/helper-mve.h
@@ -121,6 +121,8 @@ DEF_HELPER_FLAGS_4(mve_veor, TCG_CALL_NO_WG, void, env, ptr, ptr, ptr)
 DEF_HELPER_FLAGS_4(mve_vpsel, TCG_CALL_NO_WG, void, env, ptr, ptr, ptr)
 DEF_HELPER_FLAGS_1(mve_vpnot, TCG_CALL_NO_WG, void, env)
 
+DEF_HELPER_FLAGS_2(mve_vctp, TCG_CALL_NO_WG, void, env, i32)
+
 DEF_HELPER_FLAGS_4(mve_vaddb, TCG_CALL_NO_WG, void, env, ptr, ptr, ptr)
 DEF_HELPER_FLAGS_4(mve_vaddh, TCG_CALL_NO_WG, void, env, ptr, ptr, ptr)
 DEF_HELPER_FLAGS_4(mve_vaddw, TCG_CALL_NO_WG, void, env, ptr, ptr, ptr)

diff --git a/target/arm/mve_helper.c b/target/arm/mve_helper.c
index c22a00c5ed609540b0f498c35662fc4212ff8551..1752555a218ec4c0a6828e0fdd2e2ed972e08f2a 100644 (file)
--- a/target/arm/mve_helper.c
+++ b/target/arm/mve_helper.c
@@ -2218,6 +2218,26 @@ void HELPER(mve_vpnot)(CPUARMState *env)
     mve_advance_vpt(env);
 }
 
+/*
+ * VCTP: P0 unexecuted bits unchanged, predicated bits zeroed,
+ * otherwise set according to value of Rn. The calculation of
+ * newmask here works in the same way as the calculation of the
+ * ltpmask in mve_element_mask(), but we have pre-calculated
+ * the masklen in the generated code.
+ */
+void HELPER(mve_vctp)(CPUARMState *env, uint32_t masklen)
+{
+    uint16_t mask = mve_element_mask(env);
+    uint16_t eci_mask = mve_eci_mask(env);
+    uint16_t newmask;
+
+    assert(masklen <= 16);
+    newmask = masklen ? MAKE_64BIT_MASK(0, masklen) : 0;
+    newmask &= mask;
+    env->v7m.vpr = (env->v7m.vpr & ~(uint32_t)eci_mask) | (newmask & eci_mask);
+    mve_advance_vpt(env);
+}
+
 #define DO_1OP_SAT(OP, ESIZE, TYPE, FN)                                 \
     void HELPER(mve_##OP)(CPUARMState *env, void *vd, void *vm)         \
     {                                                                   \

diff --git a/target/arm/t32.decode b/target/arm/t32.decode
index 2d47f31f143f7ccc5910421af77382193237fba1..78fadef9d621890a820356b2aaa862e01f5340e0 100644 (file)
--- a/target/arm/t32.decode
+++ b/target/arm/t32.decode
@@ -748,5 +748,6 @@ BL               1111 0. .......... 11.1 ............         @branch24
       # This is DLSTP
       DLS        1111 0 0000 0 size:2 rn:4 1110 0000 0000 0001
     }
+    VCTP         1111 0 0000 0 size:2 rn:4 1110 1000 0000 0001
   ]
 }

diff --git a/target/arm/translate-a32.h b/target/arm/translate-a32.h
index 6f4d65ddb002ee374471ce2fe1bdb961a78e4b68..88f15df60e84e196bccee362372a949187aba60c 100644 (file)
--- a/target/arm/translate-a32.h
+++ b/target/arm/translate-a32.h
@@ -48,6 +48,7 @@ long neon_element_offset(int reg, int element, MemOp memop);
 void gen_rev16(TCGv_i32 dest, TCGv_i32 var);
 void clear_eci_state(DisasContext *s);
 bool mve_eci_check(DisasContext *s);
+void mve_update_eci(DisasContext *s);
 void mve_update_and_store_eci(DisasContext *s);
 bool mve_skip_vmov(DisasContext *s, int vn, int index, int size);
 

diff --git a/target/arm/translate-mve.c b/target/arm/translate-mve.c
index cc2e58cfe2f1be7758e958800b5d1cbf05c93d00..865d5acbe7673f489270dd019badb3281e7a8885 100644 (file)
--- a/target/arm/translate-mve.c
+++ b/target/arm/translate-mve.c
@@ -93,7 +93,7 @@ bool mve_eci_check(DisasContext *s)
     }
 }
 
-static void mve_update_eci(DisasContext *s)
+void mve_update_eci(DisasContext *s)
 {
     /*
      * The helper function will always update the CPUState field,

diff --git a/target/arm/translate.c b/target/arm/translate.c
index 80c282669f0d174f367d0aa3c47bd810dbf52a62..804a53279bda068215616c98c51911cb3c5b33c6 100644 (file)
--- a/target/arm/translate.c
+++ b/target/arm/translate.c
@@ -8669,6 +8669,39 @@ static bool trans_LCTP(DisasContext *s, arg_LCTP *a)
     return true;
 }
 
+static bool trans_VCTP(DisasContext *s, arg_VCTP *a)
+{
+    /*
+     * M-profile Create Vector Tail Predicate. This insn is itself
+     * predicated and is subject to beatwise execution.
+     */
+    TCGv_i32 rn_shifted, masklen;
+
+    if (!dc_isar_feature(aa32_mve, s) || a->rn == 13 || a->rn == 15) {
+        return false;
+    }
+
+    if (!mve_eci_check(s) || !vfp_access_check(s)) {
+        return true;
+    }
+
+    /*
+     * We pre-calculate the mask length here to avoid having
+     * to have multiple helpers specialized for size.
+     * We pass the helper "rn <= (1 << (4 - size)) ? (rn << size) : 16".
+     */
+    rn_shifted = tcg_temp_new_i32();
+    masklen = load_reg(s, a->rn);
+    tcg_gen_shli_i32(rn_shifted, masklen, a->size);
+    tcg_gen_movcond_i32(TCG_COND_LEU, masklen,
+                        masklen, tcg_constant_i32(1 << (4 - a->size)),
+                        rn_shifted, tcg_constant_i32(16));
+    gen_helper_mve_vctp(cpu_env, masklen);
+    tcg_temp_free_i32(masklen);
+    tcg_temp_free_i32(rn_shifted);
+    mve_update_eci(s);
+    return true;
+}
 
 static bool op_tbranch(DisasContext *s, arg_tbranch *a, bool half)
 {